The invention relates to an apparatus for fixing a toner image on a support therefor such as a recording sheet.
The wavelength of an infrared ray which gives the best percent absorption by a white paper is 3 .mu.m or higher, and a substance radiating an infrared ray with a peak in such region has a color temperature which is around 1000.degree. K. In the electrophotographic copying, a heating lamp having a wattage of about 1000 W which produces a color temperature of 2000.degree. K is usually employed in consideration of the rising rate of thermal radiation and the size of the heat source used. When such heating lamps is used and a recording sheet is passed with a speed of 8 cm/sec, the sheet may be scorched in those image portions having a substantial area, while an insufficient fixing results in line image portions.
There has been known a proposal in which a light shield member comprising a flat aluminium plate is disposed in front of an infrared lamp, and an image carrying member is passed along the light shield member in order to permit a fusion of a toner image by heating it with secondary radiation from the shield member. However, the thermal efficiency of such apparatus is not considered to be favorable because of the interposition of the secondary radiating member for direct heating of the image carrying member. In addition, where the image carrying member comes to a halt as by a failure of a conveying machine, there is a likelihood of producing a fire as a result of overheated recording sheet.